Machine for packaging articles with heat-shrinkable film

ABSTRACT

A machine for packaging products (11) with film (12) made of heat shrinkable material, comprises a body (13) containing a lower portion (14) of a shrinkage chamber which houses, wrapped in film (12), a product (11) to be packaged, and a cover (16), hinged to said body (13) and defining an upper portion (17) of the shrinkage chamber. Disposed in the shrinkage chamber (14, 17) are a heating unit (22) and a ventilating unit (26, 27) to create air circulation (29, 30, 31) inside said chamber. The ventilating unit (26, 27) is situated above the heating unit (22) to generate, when in operation, at least a flow of air (31) through the heating unit (22) in the direction of the bottom of the shrinkage chamber (14, 17).

This invention refers to a machine for packaging products with film madeof heat-shrinkable material. According to this technique, the product tobe packaged is wrapped in a film of heat-shrinkable material and placedinside a packaging machine, where the film is sealed and heat-shrunk toenclose the product. The heat required to thermally treat the film isgenerated by electric heating units disposed in a suitable positioninside the compartment receiving the product. An example of thesemachines is shown in FR-A-2,397,329.

There are known packaging machines in which special fans are disposed onthe bottom of the compartment (see FR-A-2,342,894) below the heatingunit and the surface supporting the product to be packaged, to create acirculation of air in the compartment in order to distribute the heatover the entire surface of the film.

Despite endeavours made to improve the circulation of the hot air in thecompartment, the positioning of the fans according to the knowntechnique does not allow the air to flow evenly enough over the entiresurface of the film wrapped around the product. In particular, the lowerpart of the compartment tends to remain colder than the upper part, dueto the tendency of the heat produced by the heating element to migrateupwards by convection. This can result in packaging of an unsatisfactoryquality. Unevenness in the distribution of the heat also means that, inorder to reach, in the lower part of the compartment, at least theminimum temperature required to shrink the film, the temperature in theupper part is considerably higher, resulting in an evident waste ofenergy.

A further drawback of the known machines is that, when the operatoropens the cover to remove the packaged product, he is inundated by alarge quantity of hot air escaping from the compartment. Moreover, sincethe fan is located in the lower part of the compartment, where dust andother particles of dirt easily accumulate, it inevitably whips up saiddust which ends up by blowing onto the operator when he opens the cover.For example, parts of the product to be packaged may fall to the bottomof the compartment and be crushed by the rotating fan and be hurleddangerously at the operator.

The general scope of this invention is to obviate the aforementionedproblems by providing a packaging machine in which the heat-shrinkablefilm wrapped around the product to be packaged is evenly bathed by thehot air circulating inside the compartment, thereby saving aconsiderable quantity of energy.

A further scope of the invention is to provide a machine in which thereis no considerable emission of hot air when the compartment is opened.

These scopes are achieved according to the invention by providing amachine for packaging products with film made of heat shrinkalematerial.

The innovative principles of this invention and its advantages withrespect to the known technique will be more clearly evident from thefollowing description of a possible exemplificative embodiment applyingsuch principles, with reference to the accompanying drawings, in which:

FIG. 1 shows a cutaway side view of a packaging machine according to theinvention.

FIG. 2 shows a view similar to that of FIG. 1, but in the operatingcondition, with the cover closed.

FIG. 3 shows a view similar to that of FIG. 1, referring to a differentembodiment of the machine according to the invention.

With reference to FIG. 1, a machine for packaging products 11 by meansof film 12 made of heat-shrinkable material is generically indicated byreference 10.

The machine comprises a body 13 containing a lower portion 14 of ashrinkage chamber which houses, inserted between two layers of the film12, a packet 11 to be packaged. Disposed in this portion of the chamberis a perforated support 15, advantageously a grille to support thepacket 11 while at the same time allowing the air to flow towards thesurface of the film covering the lower face of the packet.

Hinged onto the body 13 is a cover 16, which defines an upper portion 17of the shrinkage chamber. The cover 16 is provided with a handle 18 toenable it to be opened and closed by an operator.

Body 13 and cover 16 are also provided with respective opposing sealingelements (for example a blade 19 and a corresponding contrast 20), whichare brought into contact with each other when the cover is closed toobtain a thermal seal 21 of the two layers of film 12, as can be clearlyseen in FIG. 2.

Disposed in the lower portion 14 of the shrinkage chamber,advantageously in correspondence with its rear portion, is a heatingunit 22 consisting of electric elements controlled by a thermostat.

As can be seen in FIGS. 1 and 2, the heating elements 22 are containedin a rear chamber 23, separated by means of a partition wall 24 from therest of the portion 14 of the compartment housing the product to bepackaged so as to communicate with it only from below.

The rear chamber 23 is also separated from the upper portion 17 of theshrinkage chamber by means of an openable door 25, hinged to the body ofthe machine. Suitable cam-operating means, not shown in the figure inthat they are well known to the expert in the field, are disposed on thecover 16 to control the closing and opening of the door 25 when thecover is raised and lowered, respectively. The two positions are shownrespectively in FIG. 1 and in FIG. 2.

According to the innovative principles of this invention, a fan 26,operated by a motor 27, is disposed above the heating elements 22 tocreate a circulation of air inside the shrinkage chamber. Theventilating unit 26 is controlled in a known way by a microswitch toautomatically come into operation when the cover 16 is closed and tostop when it is opened.

A brief description will be given below of the operation of thepackaging machine according to the invention. Once the product 11 to bepackaged, wrapped in the film 12, has been placed on the support 15 ofthe shrinkage chamber 14, 17, the cover 16 is lowered, by operating thesealing elements 19, 20 and automatically controlling the opening of thedoor 25 and the starting up of the fan 26. The fan has vanes 28 shapedin such a way as to create an axial flow of air suctioned from theinside of the shrinkage chamber, schematized in FIG. 2 by means of thearrows 29. The air suctioned axially by the fan is transmitted bycentrifugal action towards the upper portion 17 of the shrinkage chamber(arrows 30), and towards the chamber 23 which contains the heating unit22 (arrows 31).

The airflow 31 is heated by flowing across the heating elements 22,thereby enabling the hot air to also reach the lower portion 14 of theshrinkage chamber. In the packaging machine according to the invention,the hot air is consequently distributed in a substantially uniformmanner over the entire surface of the film 12, resulting in an optimalpackaging and saving a considerable amount of energy both in generatingthe heat and in creating the airflow.

Its greater efficiency with respect to the known machines also makes itpossible to reduce or eliminate the thermal insulation on the lower partof the shrinkage chamber. In particular, the latter can be made with aperfectly smooth bottom which can therefore be easily cleaned of anydeposits of products to be packaged.

Once the packet 11 has been packaged, the cover 16 is raised, therebycausing the fan 26 to stop and the door 25 of the heating chamber 23 toclose.

It should be noted that when the door 25 is closed it prevents the heatgenerated by the heating elements 22 from passing into the upper portion17 of the compartment housing the packet and from there escaping to theoutside, where the operator is working. Moreover, the residual inertialrotation of the fan in the instants following the opening of the covercreates a slight suction of the hot air in the upper portion of thecompartment, helping to prevent it from escaping to the outside.

The disposition of the fan in correspondence with the upper portion ofthe shrinkage chamber makes it possible to achieve considerablestructural simplification of the body of the machine.

Moreover, the position of the fan prevents the particles of dirtdeposited on the bottom of the shrinkage chamber from being whipped up,thereby preventing the operator from being showered with them uponopening the cover.

In the embodiment shown in FIGS. 1 and 2, the motor-fan unit 26, 27 isfitted on the lid 16, in correspondence with its rear wall. The entireunit is consequently movable together with the cover.

The fan and the motor can also be made integral with the body of themachine, as shown in the variation of the embodiment of FIG. 3, wherefor convenience the corresponding elements or elements similar to thoseof the previous embodiment are indicated with the same numbering,increased by 100. In this case, in correspondence with its rear part,the cover 116 can be either completely or partially open, so as to avoidinterference with the motor 127 and the fan 126. It is obvious that,depending upon the structural variation chosen, the machine must beprovided with the most appropriate structural devices, obvious to theexpert in the field, to ensure the correct support of the motor-fanunit.

The foregoing description of an embodiment applying the innovativeprinciples of this invention is obviously given by way of example inorder to illustrate such innovative principles and should not thereforebe understood as a limitation to the sphere of the invention claimedherein. For example, the ventilating unit 26, 126 can be composed ofseveral fans, each operated by its respective motor 27, 127. Moreover,the fans can be equipped with vanes having a different configuration,provided that they are capable of creating inside the shrinkage chambera circulation of air qualitatively similar to that shown in FIG. 2. Forexample, radial fans can be used, or centrifugal fans with forwardinclined vanes, etc.

I claim:
 1. A machine for packaging products (11) with film (12) made ofheat shrinkable material, comprising a body (13, 113) and a cover (16,116) hinged to said body to define a shrinkage chamber between them,said chamber housing, wrapped in film (12), a product (11) to bepackaged and being provided with a supporting element (15, 115) for thefilm-wrapped product (11), said body and said cover defining,restectively, a lower portion (14, 114) and an upper portion (17, 117)of the shrinkage chamber, at least an air passage (23, 123) beingprovided between said upper and lower portions of the shrinkage chamber,the packaging machine further comprising a heating unit (22, 122) and aventilating unit (26, 27, 126, 127) arranged in said shrinkage chamberto create hot air circulation (29, 30, 31) surrounding the product (11)to be packaged, with air paths (31) connecting the upper portion (17,117) to the lower portion (14, 114) of the shrinkage chamber along saidair passage (23, 123) the ventilating unit (26, 27, 126, 127) beingdisposed in the upper portion (17, 117) of the shrinkage chamber andabove the heating unit (22,122), and the heating unit being disposedbetween the ventilating unit (26, 27, 126, 127) and the bottom of theshrinkage chamber and within a rear heating chamber (23, 123) formingsaid air passage (23, 123), the rear heating chamber (23, 123) beingseparated from the supporting element (15, 115) and the product to bepackaged by means of a wall (24, 124).
 2. Packaging machine as claimedin claim 1, characterized in that the heating chamber (23, 123)communicates from below with the lower portion (14, 114) of theshrinkage chamber and from above, through an aperture closable by meansof a door (25, 125), with the upper portion (17, 117) of the shrinkagechamber.
 3. Packaging machine as claimed in claim 1, characterized inthat the ventilating unit (26, 27, 126, 127) is disposed incorrespondence with the upper portion (17, 117) of the shrinkagechamber.
 4. Packaging machine as claimed in claim 1, characterized inthat the ventilating unit is composed of at least one fan (26, 126)operated by a corresponding motor (27, 127) and provided with vanes (28,128) capable of generating within the shrinkage chamber (14, 17, 114,117), upon closure of the cover (16, 116), circulation of air consistingof a substantially axial suction flow (29) and substantially radialflows (30, 31) directed respectively towards the upper portion (17, 117)of the shrinkage chamber and towards the lower portion (14, 114) of saidchamber, passing through the heating chamber (23, 123).
 5. Packagingmachine as claimed in claim 1, characterized in that the operation ofthe ventilating unit (26, 27, 126, 127) is controlled by the closedposition of the cover (16, 116).
 6. Packaging machine as claimed inclaim 2, characterized in that the door (25, 125) is made to open byclosing the cover (16, 116) and to close by opening said cover. 7.Packaging machine as claimed in claim 1, characterized in that theheating unit (22, 122) is composed of electric heating elementscontrolled by a thermostat.
 8. Packaging machine as claimed in claim 3,characterized in that the ventilating unit (26, 27) is integral with thecover (16), and fitted in correspondence with a rear wall of the latter.9. Packaging machine as claimed in claim 3, characterized in that theventilating unit (126, 127) is integral with the body (113) of themachine, the cover (116) being open in correspondence with its rear wallfor its free movement with respect to the ventilating unit. 10.Packaging machine as claimed in claim 1, characterized in that, disposedin the lower portion (14, 114) of the shrinkage chamber is a perforatedsupport (15, 115) to support the product (11) to be packaged, allowingthe passage of air towards the surface of film (12) covering the productin correspondence with said support (15, 115).